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Thermal Expansion of the Orthorhombic Phase in the Ln 2 TiO 5 System
Author(s) -
Seymour Kevin C.,
Hughes Robert W.,
Kriven Waltraud M.
Publication year - 2015
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.13821
Subject(s) - orthorhombic crystal system , thermal expansion , trigonal bipyramidal molecular geometry , crystallography , phase (matter) , materials science , trigonal crystal system , synchrotron , thermal , x ray crystallography , diffraction , chemistry , mineralogy , crystal structure , thermodynamics , optics , physics , metallurgy , organic chemistry
The thermal expansion behavior of the orthorhombic phase in the Ln 2 TiO 5 (Ln = La, Nd, Gd, Dy, and Y) system was evaluated, using synchrotron X‐ray diffraction from room temperature to approximately 1500°C in air. The components of the thermal expansion tensor were calculated from the refined d‐spacings, using the program CTEAS. Subsequent analysis of the thermal expansion and crystallographic information revealed that the mechanism behind the thermal expansion was a result of strained trigonal‐bipyramidal structures overcoming an energy barrier to become more relaxed. The temperature at which a significant shift in the trigonal‐bipyramidal structure manifests was correlated with the size of the rare‐earth cation that dictates the volume of the overall cell. Larger rare‐earth cations with larger cell volumes allow more room for the trigonal‐bipyramidal structures to easily relax.